As debate grows about a possible second stimulus package for the flagging American economy, at least one legendary investor is giving the idea his guarded approval.

"I think that a second one may well be called for," Warren Buffett, the CEO of Berkshire Hathaway, told "Good Morning America" today. But, he added, "you hope it doesn't get watered down in many ways."

Buffett cautioned that a second stimulus package, like the first, won't be "a panacea," because stimulus packages take time to work. He criticized lawmakers' work on the first stimulus package, which contained $787 billion in spending.

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"Our first stimulus bill ... was sort of like taking half a tablet of Viagra and having also a bunch of candy mixed in ... as if everybody was putting in enough for their own constituents," he said. "It doesn't have really quite the wall that might have been anticipated there."

Buffett also criticized the government's public-private investment plan, through which private investors are supposed to buy so-called toxic assets off the balance sheets of ailing banks that received billions in government aid.

"I do not like the idea of any kind of a plan involving the government where Wall Street makes a lot of money. My plan provided that they would make no money whatsoever, and the American public would make the money. I just think that Wall Street owes the American people one at this point," he said.

Nebraska native Buffett, known as the "Oracle of Omaha" for his long history of prescient stock picks, said that despite the talk of recent economic "green shoots," he couldn't predict when the flagging economy would bounce back.

"We are not in a freefall, but we are not in a recovery either," Buffett said. "We were in a freefall really in the last quarter of last year, starting in the financial markets and spreading to the economy, and we had this huge change in behavior. That change hasn't changed."

The U.S. unemployment rate, which currently stands at 9.5 percent, still "has a ways to go" before it peaks, he said. His own company, he said, had to lay off 500 people.

"We didn't want to do it, and if we saw things coming back we wouldn't do it," he said.

Warren Buffett: Recession a 'Shock to the System'

Buffett said he's never seen a recession affect consumers the way the current one has.

"I have never seen it quite happen like this, but what happened was in late September, the American public … saw money market funds break the buck. They saw commercial papers stop, they saw all kinds of things that they hadn't seen before," he said. "It was a shock to the system."

Still, Buffett remains optimistic.

"I want to emphasize, we are going to come out of this better than ever," he said. "I mean the best days of America, by far, lie ahead. But not next week or next month and then, I don't know exactly when we will come out, but we will come out big time."

Second Stimulus Debate Grows

Talk of a second stimulus has grown, as the economy shows limited signs of improvement.

"It looks like the economy is weaker than expected. Why not begin to think about over the next several months whether we need a stimulus package and what it should include," Laura D'Andrea Tyson, Obama's economic adviser said recently.

Some, including Nobel Prize-winning economist Paul Krugman, support the second stimulus idea, but Republicans doubt it will yield any results.